1. Field of the Invention
This invention relates to a method of forming a nozzle for an ink-jet printer head which ejects ink droplets to write records.
2. Prior Art
An ink-jet printer head ejects ink in the form of ink droplets from a nozzle to write records on a recording medium. In the case where water base ink is used as the ink, when the periphery of an opening of the nozzle has insufficient water repellency, the ink is liable to stick to the surface of the opening, thereby suffering a problem in that the straightforwardness of ink droplets is impaired.
It is generally understood that, with respect to the water repellency of the periphery of a nozzle opening, a contact angle of 90 degree or more does not cause the straightforwardness of ink droplets to be impaired. Accordingly, the surface of a nozzle opening is usually coated by a water repellent agent.
As the method of forming such a coating layer, there have been proposed various methods such as the electrostatic spray coating method (Japanese Patent Unexamined Publication (Kokai) No. SHO 57-167765), the vacuum deposition method (Japanese Patent Unexamined Publication (Kokai) No. SHO 60-183161), the dipping method, the spray coating method, and the spin coating method, etc. All of these methods have a drawback that a water repellent agent may enter a nozzle to clog it or to impair the straightforwardness of ink droplets, thereby adversely affecting the printing quality.
As a method of providing the water repellency to a surface of a nozzle opening without causing the nozzle to be clogged, Japanese Patent Unexamined Publication (Kokai) No. SHO 63-122560 discloses a method in which a flow path for ink is previously filled with a liquid or solid material and the coating process is then conducted, and Japanese Patent Unexamined Publication (Kokai) No. SHO 62-59047 discloses a method in which the coating process is conducted while ejecting air from a nozzle.
However, the former method has problems in that it is not easy to fill the flow path with a liquid or solid material and also that it is difficult to remove an excess of the filler material while keeping the flow path filled with the filler material. The latter method has a problem in that the periphery of the nozzle opening in which the water repellency must be exerted at the highest degree is affected by the air stream so as not to be sufficiently coated.
On the other hand, Japanese Patent Unexamined Publication (Kokai) No. HEI 3-207657 proposes a method in which an excimer laser is used as a nozzle forming means. This publication discloses also that, at the same time when a nozzle is formed, a water repellent layer formed on the periphery surface of the nozzle opening is removed by an excimer laser. Teflon may be used as a water repellent agent which can be removed by an excimer laser, but has a drawback that, when wiped, it is easily peeled off from the surface of the nozzle. A silicone resin cannot be superposed on a resin which can be ablated by an excimer laser. A silicone resin can be strongly bonded to glass. When glass is used as the material of the nozzle forming member, however, there arise problems in that it is difficult to form a nozzle and that glass dissolves in a long-term use.